3D Stacking Structure and Method of Fabricating the Same

Abstract

A method includes forming a first package component and a second package component. The first package component includes a first polymer layer, and a first electrical connector, with at least a part of the first electrical connector being in the first polymer layer. The second package component comprises a second polymer layer, and a second electrical connector, with at least a part of the second electrical connector being in the second polymer layer. The first package component is bonded to the second package component, with the first polymer layer being bonded to the second polymer layer, and the first electrical connector being bonded to the second electrical connector.

What is claimed is: 
     
         1 . A method comprising:
 forming a first package component comprising:
 a first polymer layer; and 
 a first electrical connector, with at least a part of the first electrical connector being in the first polymer layer; 
   forming a second package component comprising:
 a second polymer layer; and 
 a second electrical connector, with at least a part of the second electrical connector being in the second polymer layer; and 
   bonding the first package component to the second package component, with the first polymer layer being bonded to the second polymer layer, and the first electrical connector being bonded to the second electrical connector.   
     
     
         2 . The method of  claim 1 , wherein the first polymer layer comprises a first polymer chain, and the second polymer layer comprises a second polymer chain, and wherein the first polymer chain and the second polymer chain are joined to form a long polymer chain. 
     
     
         3 . The method of  claim 1 , wherein the first electrical connector and the second electrical connector are bonded through solder bonding. 
     
     
         4 . The method of  claim 3 , wherein the bonding comprises:
 putting the first package component into contact with the second package component;   performing a pre-heating process at a first temperature;   performing a solder reflowing process to reflow a solder region, wherein the solder reflowing process is performed at a second temperature higher than the first temperature; and   performing an annealing process at a third temperature.   
     
     
         5 . The method of  claim 4  further comprising, before the first package component is put into contact with the second package component, partially curing the first polymer layer and the second polymer layer, wherein in the annealing process, the first polymer layer and the second polymer layer are fully cured. 
     
     
         6 . The method of  claim 4 , wherein the first temperature is lower than a melting temperature of the solder region. 
     
     
         7 . The method of  claim 1 , wherein the first electrical connector and the second electrical connector are bonded through direct metal-to-metal bond. 
     
     
         8 . The method of  claim 7 , wherein the bonding comprises:
 a pre-heating process at a first temperature;   a heating process to form the direct metal-to-metal bond, wherein the heating process is performed at a second temperature higher than the first temperature; and   an annealing process at a third temperature.   
     
     
         9 . The method of  claim 1 , wherein the first electrical connector is recessed from the first polymer layer to form a recess, and the second electrical connector comprises a protruding portion protruding out of the second polymer layer, and wherein in the bonding, the protruding portion extends into the recess. 
     
     
         10 . The method of  claim 9 , wherein the recess is formed by processes comprising:
 applying the first polymer layer, wherein a portion of the first polymer layer covers the first electrical connector;   planarizing the first polymer layer; and   performing a photolithography process to remove the portion of the first polymer layer.   
     
     
         11 . The method of  claim 9 , wherein the protruding portion is formed by processes comprising:
 applying the second polymer layer, wherein a portion of the second polymer layer covers the second electrical connector;   planarizing the second polymer layer; and   etching back the second polymer layer.   
     
     
         12 . A structure comprising:
 a first package component comprising:
 a first polymer layer; and 
 a first electrical connector, with at least a part of the first electrical connector being in the first polymer layer; and 
   a second package component comprising:
 a second polymer layer bonding to the first polymer layer; and 
 a second electrical connector, with at least a part of the second electrical connector being in the second polymer layer, wherein the first electrical connector is bonded to the second electrical connector. 
   
     
     
         13 . The structure of  claim 12 , wherein the first polymer layer and the second polymer layer comprise different polymers. 
     
     
         14 . The structure of  claim 12 , wherein the first polymer layer and the second polymer layer comprise a same polymer material, and wherein the first polymer layer and the second polymer layer have a distinguishable interface. 
     
     
         15 . The structure of  claim 12 , wherein the first polymer layer comprises a first polymer chain, and the second polymer layer comprises a second polymer chain, and wherein the first polymer chain and the second polymer chain are joined to form a long polymer chain. 
     
     
         16 . The structure of  claim 12 , wherein the second electrical connector comprises a protruding portion in the first polymer layer. 
     
     
         17 . A structure comprising:
 a first package component comprising:
 a first surface dielectric layer; 
 a first metal pillar protruding out of the first surface dielectric layer; and 
 a first polymer layer encircling the first metal pillar; and 
   a second package component comprising:
 a second surface dielectric layer; 
 a second metal pillar protruding out of the second surface dielectric layer; and 
 a second polymer layer encircling the second metal pillar, wherein the first metal pillar is electrically coupled to the second metal pillar, and wherein the second metal pillar further extends into the first polymer layer. 
   
     
     
         18 . The structure of  claim 17  further comprising a solder region physically joining the first metal pillar to the second metal pillar, wherein the solder region includes at least a part in the first polymer layer. 
     
     
         19 . The structure of  claim 18 , wherein the first metal pillar comprises first straight sidewalls contacting the first polymer layer, and the solder regions comprise second straight sidewalls contacting the first polymer layer. 
     
     
         20 . The structure of  claim 19 , wherein the second straight sidewalls are aligned to the first straight sidewalls.